Kids ask: How do birds make red blood cells

This red-tailed hawk was saved by veterinary students at the University of Illinois after being rescued by a staff member. The bird cannot live in the wild so it will be a permanent resident at the school's Wildlife Medical Clinic.Courtesy University of Illinois College of Veterin

Students in Polly Kluver's seventh-grade science class at West Oak Middle School in Mundelein asked: "How do birds make red blood cells if their bones are hollow?"

Bird lovers, you might not realize it, but you belong to a very large club.

About 20 percent of Americans enjoy the sport of bird watching, an easy, low-cost hobby that can start in your own back yard and take you far across the globe in search of exotic species. More U.S. bird enthusiasts live in the South, but local websites like ilbirds.com and illinoisbirds.com point to a huge flock of bird enthusiasts residing here in the Chicago area.

Streamlined for flight, birds have fewer bones than other vertebrates. Beaks are designed as a lightweight adaptation that replaces a heavier jaw structure, and wing bones are constructed sparingly to aid in flight. The major limb bones are hollow, decreasing overall weight, but built for strength.

"Like mammals, birds make red blood cells in their bone marrow but not all the bones have the same amount of marrow," said veterinarian Julia K. Whittington, medical director of the Wildlife Medical Clinic at the University of Illinois College of Veterinary Medicine in Urbana. "Pneumatic bones, those that are hollow and communicate with the bird's air sac system and respiratory tract, only have cancellous bone at the ends or epiphyses. Cancellous bone is the site of blood cell production," Whittington said.

Good samaritans looking to help nurse a wild animal back to health can bring birds or other wild animals to the university's Wildlife Medical Clinic. The clinic serves about 1,500 wild animals each year.

The wildlife clinic sees any ill or injured wild bird brought in by the public including birds of prey like hawks, eagles and owls; waterfowl like ducks and geese; songbirds, such as robins, sparrows and finches; and nonnative migratory birds like cranes and even a pelican, Whittington said.

"The clinic is open year round, and no wild animal patients are refused. The clinic is a nonprofit organization depending entirely on donations and grants for funding its work."

Some animals, like the red-tailed hawk in the photo, regain their health but are not able to survive in the wild, so they remain in residence at the clinic.

Go behind the scenes at the state's only veterinary college on Sunday, Oct. 3, from 10 a.m. to 4 p.m. at the free Vet Med Open House in Urbana. The theme is "Explore Your Animal Instincts." The program offers more than 40 exhibits and demonstrations. Vet students host this event. For more information see the U of I College of Veterinary Medicine website at vetmed.illinois.edu.

Check these out

The Fremont Public Library District in Mundelein suggests these titles on birds: